Not Applicable
Not Applicable
1. Field of the Invention
This invention relates to spot welder tip sharpening and dressing tools and particularly to spot welder tip sharpening and dressing tools that are hand held.
2. Description of the Prior Art
Spot welding machines have been used for years to make simple, fast welds in metals. These machines range from small welders typically handled by one or two people to huge robotic machines that can weld large workpieces. Despite the differences in size, all electric spot welders work on the same basic principal: a pair of electrodes positioned to allow a workpiece to be positioned between them. A mechanism causes the electrodes to be brought together. Electric current then flows between the electrodes and the workpiece causing the metal at that point to be fused. The electrodes are released and the workpiece can be removed.
The electrodes used in spot welding are typically copper. They are formed into a point that has a slightly rounded tip. After a certain number of welds, the tips of the electrodes become worn and flattened. When this happens, the electrodes are no longer able to xe2x80x9cspotxe2x80x9d the electric current in a small enough space to form a good weld. Although electrodes can be replaced once this happens, replacement becomes costly, especially when the electrodes last for only 50 or 60 welds. To prolong the use of the electrodes, the tips can be sharpened and dressed. In small shops, this process involves using a file to hand-shape the electrode tips. This not only takes time; it also takes a degree of skill. The electrodes must be sharpened to the right angle and symmetrically for optimum performance. If the job is done poorly, the electrodes may be ruined and have to be discarded.
For larger machines, hand dressing is impractical. These machines often run 24 hours a day and require several dressings. Several machines have been developed to address this need. For example, U.S. Pat. Nos. 5,993,125, 6,195,860, 6,106,203, 5,332,342, 5,288,185, 4,610,153 and 4,966,506, teach complex devices for dressing electrode tips. These machines have a cutting element that is secured in a drive mechanism. This cutting element is then used to dress the tips in large and robotic spot welding machines. These devices are not intended for use on small welders, such as those found in small sheet metal shops.
U.S. Pat. Nos. 4,966,504, 4,921,377, and 4,856,949, teach tools that can be used to dress electrode tips. These tools are typically a set of cutters placed in a holder that is then turned by some mechanical means. The shape of the cutters is designed to permit both electrodes to be dressed simultaneously. These cutters are typically designed to be used in the machines discussed above. However, they could be used in smaller devices provided a proper drive system was used.
One U.S. Patent appears to be directed to small welding machines. U.S. Pat. No. 4,578,005 teaches a manual type tool. This tool has a long handle, like a wrench. It has a head that contains the cutting tools. The head is ratcheted within the handle. The cutters have edges on both top and bottom so that both electrodes can be dressed simultaneously. The tool is used by placing it between the electrodes, clamping the electrodes together and then turning the handle. Because of the ratchet, the head turns in one direction only. The tool is thus manipulated until the desired degree of dressing is established.
There are some problems with this tool. First, the tool must be held level to obtain a proper tip formation. Because a single handle is used to hold the cutters, it is very difficult to ensure the cutter head remains truly level with respect to the electrodes. Moreover, the use of the manual drive not only increases the time involved, but also increases the risk that the electrodes will be either over dressed or underdressed.
Thus, a small serviceable tool for dressing electrode tips on small welders is needed.
The instant invention overcomes all of the difficulties mentioned above. It is a powered rotary drive unit that has two handles. The operator places the cutters between the electrodes and applies clamping pressure. The operator then activates the motor to dress the electrodes. The cutter is designed to cut the electrodes to the proper shape so that the tips cannot be over-dressed. Moreover, the two handles insure that the cutters remain level during the entire dressing operation. Finally, the cutters are ground to a specific angle that improves the performance of the welder by flattening the tips to an optimum angle.